The invention concerns a blind riveter with a tension chuck, a hydraulic system for moving the tension chuck, and a pneumatic system with a cylinder and piston whereupon under power stroke of the piston a movable piston rod is moved in the hydraulic system, and with a valvular arrangement for the compressed air supply, which is operable through a longitudinally sliding valve tappet.
According to the German patent document No. 1,217,175, such a blind riveter is known. The arrangement of its valves, and valve tappet are accommodated in a region of the implement's casing, the region being essentially designed as a massive lateral extension of one piece continuous with the wall of the pneumatic cylinder. This region of the casing extends from the region of the inlet side of the pneumatic cylinder to almost its opposite side, whereby a portion of this addition is forked and serves as a swivel bearing for the operational element for the valve tappet. The remaining extension gives rise to a continuous longitudinal enlargement which diameter is stepped two times and which walled off end to the operational element transforms into a threaded sleeve into which a compressed air connection is screwed. The region of the largest diameter is linked up with the threaded sleeve in which a valve plate with play in all directions is accommodated. From the connecting middle section of the enlargement in the direction of the operational element, a slanting bore hole of proper diameter is in position to pass through the extension of the casing into the inside of the cylinder. The remaining portion of the enlargement corresponds to the thickness of the valve tappet in the sliding seat fit. The valve tappet is designed as a tube, both sides being open, one of which however the walling is pulled in and serves to brace a tension spring, which is accommodated inside the tube. The spring butts against the valve plate through the opposite end of the tube. On the opposite surface of the valve plate, a spring of that kind in the compressed air connection acts, in its resting position, so that the valve plate presses on the passage between the region of the enlargement with the middle and largest diameter, so that it rests thereagainst in an airtight manner. By swiveling of the operational element this spring becomes compressed so that the free end of the valve tappet pushes against the valve disc and shoves this so far that compressed air reaches into the middle region of the enlargement, around the valve disc, and reaches the inside of the cylinder through the bore hole. Thereby the piston of the pneumatic system is set in motion, influences the hydraulic system and causes a blind rivet to be set. As soon as the operational element is released, the spring in the valve tappet can push this away from the valve plate. The opposing spring becomes activated and closes the compressed air supply. Simultaneously, the pressure in the hydraulic system becomes equalized through the return set spring, and the piston of the pneumatic system is pushed back. The compressed air in the cylinder of the pneumatic system between the piston and the hydraulic system can escape through an exit aperture. The air behind the piston, compressed through the return motion, logically then in the end of the cylinder, can escape through the slanted bore hole, the middle section of the clearance and the interspace between the valve plate and the end of the valve tappet. The additional casing outside the pneumatic cylinder of this known implement represents an enlargement of its bulk and increase of its weight. The latter becomes especially uncomfortably noticeable as moment of stress by the appearance of fatigue through the arrangement at the end of the casing, i.e., the farthest possible distance from that region which is handled by the operator. In the fabrication the form of the casing is expensive due to the stepped clearance and especially because of the slanting bore holes. The out flow of air created by the returning piston found on the backside thereof becomes impeded through the arrangement of the end of the valve tappet serving as an out flow aperture on the operational element, and results in resistance to the return motion, which is undesirable on the known blind riveter, since the entire return set motion there is conducted by one single spring.
The task of this invention is to create a blind riveter of previous described type, which arrangement of valves and tappets is simple and is arranged without additional weight and increased dimensions.